An Added Bonus of Solar Panels: They Keep Buildings Cool
Solar panels don't only convert sunlight into energy. They also help cool the roofs and buildings that they grace.
When New York rolled out a solar map of the city, I wrote that, as a renter, I didn’t have a strong financial incentive to urge my landlord to go solar: I’d only save about $31 each year. But a new study from the University of California at San Diego suggests there’s another incentive for installing solar panels on a building, particularly for someone who lives on the top floor like I do. The UC-San Diego research found that in addition to absorbing sunlight and converting it to energy, solar panels help cool roofs and buildings.
Standard black roofs soak up heat, which is transmitted into the ceilings and rooms below. This is one of the reasons why attics are so hot in the summer. It’s also one of the reasons why my apartment, on the fifth and top floor of my building, is hotter than one on the first floor.
Solar panels, of course, intercept sun rays that would otherwise heat the building, converting them into energy. When wind blows into the gap between the solar panels and the roof, it also clears away heat. Students at UC-San Diego determined that the net result of these cooling effects was that portions of a ceiling beneath solar panels were 5 degrees Fahrenheit cooler than portions beneath the open roof. Solar panels tilted at an angle had an even greater cooling effect than solar panels laid flat against the roof, because the gap between the panel and the roof allowed more air to circulate, whisking away that much more heat. More efficient solar panels, which convert more sunlight into energy, also do a better job at cooling.
Since solar panels keep heat from seeping into a building, they also help save on cooling costs over time. The UC-San Diego team calculated that over the lifetime of a set of solar panels, these savings added up to the equivalent of a 5 percent discount on the panels’ cost.
For anyone who already has solar panels installed, this finding is just an added bonus. But as Jan Kleissl, the researcher who oversaw the study, notes, if your goal is to cool a building passively, solar panels aren’t the most efficient option. White roofs, which can reflect 80 percent or more of the light that hits them, are just one way to cool a building more efficiently.
white roofs can lessen the heat inside your building on a sunny, 90-degree day, they won’t also power the fans or air conditioners that you eventually turn on to keep from melting. As a rule, though, solar panels don’t cover a roof entirely: why not opt for both? At this point in July, I’m thankful for any technology that might drop the heat a degree or two.
Photo courtesy of flickr user Steve Ryan, Creative Commons Attribution License 2.0